The objectives of this research are a better understanding of the structure and dynamics of phospholipid bilayers and the further development of generally applicable techniques for biological membrane studies. The 18 carbon conjugated tetraene fatty acid parinaric acid has been shown to be a very useful fluorescent probe for the detection and characterization of bilayer phase transitions and lipid-protein interactions. Other polyene fatty acids will be synthesized and evaluated as probes. Two polyene steroid analogs of cholesterol have been prepared and found to be fluorescent. They will be used to study the cholesterol/phospholipid phase diagram. Polyenes in membranes will be studied by resonance Raman, resonance Rayleigh and circular dichroism spectroscopy. The structure of phospholipid bilayers will be investigated by Raman spectroscopy using specifically deuterated phospholipids. Lipid-protein interactions will be studied using tryptophan to polyene energy transfer. The combined application of polarized absorption, time resolved fluorescence depolarization and resonance enhanced depolarized Rayleigh scattering will provide a complete determination of the average orientation of the acyl chain and the time dependence of its angular excursions. The Raman study will provide an unambiguous determination of the probability that a particular bond in an acyl chain is in the gauche conformation. Phase diagrams for phospholipid mixtures will be determined by fluorescence methods.